WASHINGTON (CNN) -- Sen. Hillary Clinton's one-time chief strategist wanted to attack Sen. Barack Obama for lacking "American roots" during the Democratic primary battle, according to a magazine article set to be published online Monday evening.

A Mark Penn memo reportedly said the U.S. wouldn't vote for a candidate who was not "fundamentally American."

"All of these articles about his boyhood in Indonesia and his life in Hawaii are geared towards showing his background is diverse, multicultural and putting that in a new light. Save it for 2050," Mark Penn, then Clinton's chief strategist, wrote in a March 2007 memo, according to an article to be published in the September edition of The Atlantic magazine.

"It also exposes a very strong weakness for him -- his roots to basic American values and culture are at best limited. I cannot imagine America electing a president during a time of war who is not at his center fundamentally American in his thinking and in his values," Penn wrote, according to the article by Joshua Green.

The article is expected to be available on the magazine's Web site Monday evening, The Atlantic said. The print version of the magazine is expected to hit newsstands August 19.

Green noted that Clinton did not pursue the strategy Penn suggested during the contentious Democratic primary battle, which resulted in Obama defeating the former first lady and locking up their party's presidential nomination.

In April, Penn was forced out of his position as chief strategist after revelations that he lobbied for a U.S.-Colombia trade deal on behalf of the Colombian government despite Clinton's opposition to the measure. Penn, however, never left the campaign entirely.

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In the Atlantic article, which is based on internal Clinton campaign memos and e-mail messages, Green highlighted bitter fighting among Clinton's staff, writing that her advisers "couldn't execute strategy; they routinely attacked and undermined each other and Clinton never forced a resolution."

The internal communication also suggests that the lack of clear lines of authority within the campaign meant that issues that ultimately led to Clinton's defeat -- her lack of support in the Iowa caucuses, the absence of a strategy to capture delegates after the Super Tuesday primaries and her failure to prepare for a protracted primary fight -- went unaddressed for months, Green wrote.

"What is clear from the internal documents is that Clinton's loss derived not from specific decisions she made but rather from the preponderance of the many she did not make," Green wrote. "Her hesitancy and habit of avoiding hard choices exacted a price that eventually sank her chances at the presidency."

The documents also suggest the Clinton staff remained divided throughout the campaign on whether she should run a positive campaign or attack Obama and her other rivals for the Democratic nomination as being untrustworthy and underqualified, Green wrote.

"Clinton's top advisers never agreed on the answer. Over the course of the campaign, they split into competing factions that drifted in and out of Clinton's favor but always seemed to work at cross purposes. And Clinton herself could never quite decide who was right," he wrote.